Original AD bumpers are spring steel. But they don't have to be compressed like Jerry described. They could be straightened, but it would take a big press to do it correctly. You would have to over-straighten quite a bit for it to spring back to the correct curvature. If you heat it, it will lose it's springiness, which may or may not be good (it'll be easier to bend, and provide less protection in a bumper tap.) If there's a plating shop near you, they're probably set up to do that kind of straightening. but it would be $$.
The bumper brackets are also spring steel, so the same would apply to them.
